In recent years, a LED has been used in various applications because it is considered as being energy-saving light source and having a long lifetime. For example, the LED is used as backlight source for display device (e.g., liquid crystal display). Furthermore the LED is used in camera flash applications and automotive applications, and also in various lighting applications.
The high brightness of the LED is generally achieved by an increase in an applied current to the LED, i.e., by an increase in the amount of light. The increased current applied to the LED, however, can be a severe operating condition for the LED, causing the performance of the LED to be degraded. The degradation of the LED inhibits the long lifetime and high reliability in the LED package and module. For example, when an electric current through the LED is increased, the heat attributed to the LED increases. Accordingly, the temperature tends to rise in the LED module for lighting and a system thereof, which leads to a deterioration of the LED module and the system. In this regard, only about 25% of the electric power to be consumed in the white LED is converted into the visible light and the rest of the electric power is directly converted into the heat. Therefore, it is required to release the heat from the LED package, and thus various types of heat sinks are used to this end.